Device for compartmental dilatation of blood vessels

ABSTRACT

A constraining structure for use with a balloon catheter includes multiple longitudinal struts and multiple expandable radial rings. The constraining structure can expand radially but may not expand substantially in the longitudinal direction. The constraining structure can have multiple compartments configured to expand independently of one another. Inflating the balloon catheter within the constraining structure can allow for dilation of the blood vessel in a pre determined topography.

This application is a continuation of U.S. patent application Ser. No.14/807,657, filed Jul. 23, 2015, which is a continuation of U.S. patentapplication Ser. No. 13/756,250, filed Jan. 31, 2013, which claims thebenefit of U.S. Provisional Application No. 61/593,704, filed Feb. 1,2012, the entirety of which is incorporated by reference herein.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to the field of medical methods anddevices, specifically to medical dilatation balloon catheters anddevices intended to treat blood vessel obstructions and/or deliveractive substance to body tissue.

Angioplasty balloons are one of the most commonly used tools fortreatment of narrowed and occluded blood vessels. These balloons aretypically cylindrical when inflated and are manufactured in variousdimensions (length and diameter) to conform to different vessel size.Balloons are located at the distal end of flexible catheters anddelivered to a target site/lesion where they are inflated, normallybetween 8-20 atmospheres, in order to overcome the resistance of thelesion and achieve luminal expansion. Such high pressure angioplasty isoften associated with trauma to the vessel walls with a resulting highfrequency of vessel dissection (30%-40%), abrupt closure of the treatedvessel (5%-12%), and restenosis. When conventional angioplasty is usedas a primary treatment for occluded vessels, restenosis can occur inabout 50% of the cases. Therefore in the vast majority of coronarytreatments, angioplasty is used as an initial treatment followed byplacement of a stent. Frequently the stents are coated with drug andpolymer requiring the patient to take anti platelet therapy for extendedperiods, possibly lifelong, to limit the risk of stent thrombosis orblood clots.

In a standard balloon in order for the inflation to be effective it isnecessary to apply more and more pressure until the stenosis gives way.This is an abrupt and forceful process that may result in severe traumato the vessel wall that in the best case further delays the healing ofthe lesion and in the worst and not uncommon case result in dissections,abrupt closure and restenosis.

Dissections in the treated blood vessel due to balloon dilation are verycommon. The dissection rate is estimated as high as 30% of the cases.Some of these are severe and may require urgent surgery or placement ofadditional stents. In addition, dissection may contribute to poor longterm clinical results and restenosis even if a stent is placed in thetreated lesion. Dissections are attributed to several mechanismsoccurring during balloon inflation including the shear forces applied onthe vessel walls as the balloon pleats unfold and uneven inflation ofthe balloon due to inconsistency of the disease in the vessel. Duringinflation, while the balloon diameter increases in the radial direction,the folded balloon is unwrapped and applies tangential forces (See FIGS.1A, 1B and 1C). Attempts have been made to resolve this problem byproviding fully elastic or stretchable balloons that open radiallywithout unfolding. However, those balloons, made of elastic materialscould not provide sufficient dilatation forces since the materials aresoft and compliant not capable of high pressure inflation.

The disease is not uniform and the inner diameter of the vessel can becharacterized as anisotropic. Standards angioplasty balloons arecommonly elastic or semi-compliant, and are designed to increase theirdiameter, and therefore apply force on the surrounding area in a uniformway. When inflated against an inconsistent resistance (eccentriclesions, focal plaque) it will be necessary to apply increased pressureuntil the plaque gives way and the balloon is fully inflated. Thisabrupt and uncontrolled process causes increased trauma to the area.Furthermore, at the initial stage of the elastic nature of a ballooncause its diameter to increase more at the elastic (and less diseased)areas of the vessel causing further trauma and delayed healing.

Long lesions (typical of peripheral lesions) create additionalchallenges. These lesions often require repeated inflation/deflationswhile progressing through the occluded vessel. This requires aconsistency in the quality of performance that is not typical toballoons. Furthermore angioplasty balloons lengthen during dilation (upto 10%), this may cause further damage to non-diseased areas. Since thelengthening of the balloon is relative to its length, this is especiallypronounced in treating long lesions.

Dissections, elastic recoil and abrupt closure are all mechanismsassociated with current angioplasty balloons having a high level ofinjury and trauma to the treated vessel.

Therefore, it would be desirable to provide improved balloons andinflation structures for angioplasty balloons used in vasculartreatments. In particular, a balloon that has less tendency to causetrauma and dissection to the blood vessel wall by modulating theinflation characteristics of the balloon and providing segmentalcompartmental dilation with local areas of compliance. Furthermore acontrolled inflation that allows for a slow plaque remodeling andmodification process can prove to be less traumatic and promote fasterhealing of the lesion.

It would be further desirable if the reduced dissections could alsoreduce the risk of elastic recoil and abrupt re-closure which areassociated with current angioplasty balloons and their use. It would befurther desired if such improved angioplasty balloon structures werecompatible with each of stents, drug-eluting stents, and drug coatedballoons. These advantages would preferably be obtained without loss ofthe ability of the catheters to increase the luminal size and restoreblood vessel in the patient being treated. At least some of theseobjectives will be met by the invention as described hereinafter.

SUMMARY OF THE INVENTION

This invention discloses a device for angioplasty or dilatation ofstenotic vessels and optionally for the delivery of active substance tothe vessel wall. The balloon catheter disclosed here is designed tosupport a controlled and regulated plaque remodeling process promotingfaster healing of the diseased area. This is achieved by modulation ofthe inflation characteristic resulting in less trauma to vessel wallduring inflation.

This balloon catheter consists of a balloon catheter and a ConstrainingStructure (CS) located on the balloon portion of the catheter. TheConstraining Structure (CS) serves to control and limit ballooninflation by modifying balloon topography and creating compartmentalinflation where each inflation zone is independent of neighboring zones.This topography helps to promote plaque remodeling during inflation andallow for a controlled inflation with minimized trauma to vessel wall.The CS also inhibits transfer of shear forces to the lesion and vesselwall as the balloon inflates.

As the balloon inflates both balloon and CS structure increase indiameter however the CS maximal diameter is smaller than the balloondiameter. The balloon continues to inflate through the CS creating atopography of hills (pillows) and valleys (CS locations). The CS andballoon are capable of expanding due to inflation force applied byballoon dilation. The CS expansion is limited by its geometrical design.The CS is designed to limit balloon diameter, to eliminate transfer oftangential forces to vessel wall and to allow a plaque remodelingprocess that minimizes trauma and promotes faster healing.

A conventional balloon is compliant or semi-compliant and has a smootheven surface. During inflation the balloon will expand more easily inareas of less resistance, such as the less diseased areas (see Image 4Ato 4C). In order to successfully open the lesion it is necessary toapply more pressure then when pressure is high enough the lesion will“give in” and open abruptly. This inflation process is fast andaggressive and may cause severe trauma. The device described in thisinvention is designed to allow a slow process of plaque remodeling wherethe plaque is able to flow and reshape itself due to the topographycreated by the CS. It creates a series of cushions where the CS islocated at valleys between them (see FIG. 3). The CS channels betweenthe cushions prevent high pressure buildup in the plaque and overexpansion of the dilated vessel thus minimizing trauma caused to vesselwalls during inflation. Thus the inflation process is controlledresulting in less trauma to the vessel and faster healing of the area.

The CS is situated over the deflated and folded balloon and attached tothe catheter near the distal end of the balloon or near the proximal endof the balloon or preferably both. It also can be placed over theballoon without attachment. Upon balloon inflation the CS expands andallows the dilatation of the vessel by the balloon in a pre determinedtopography. During balloon dilation both the balloon and the CSstructure increase in diameter while length of the device does notchange. This further modulates the mechanics of inflation by minimizingthe creation of axial tension forces on the vessel wall. Unlikeconventional balloons where the length of the balloon will increase upto 10% during inflation the CS structure and balloon effective length donot change. When balloon length is maintained throughout the inflationprocess it allows predictability and more control of the inflationmechanism, and the healthy areas of the vessel are not exposed toinflation and tension forces exposing them to further damage.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1A to 1C show a cross-section of the stages of unwrapping ofconventional balloon inflation in a stenotic blood vessel.

FIGS. 2A and 2B show this invention where a Constraining Structure islocated on the balloon creating a controlled topography of hills andvalleys during inflation.

FIGS. 3A to 3C show a cross-section of the dilatation device in thisinvention during 3 different stages of inflation while unwrapping occurwithin the constraining device.

FIGS. 4A to 4C show 3 inflation stages of a conventional balloon.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

This invention discusses a device for treating of diseased, blocked,occluded or stenotic lumens in the body, typically blood vesselsincluding both arteries and veins, and more typically coronary andperipheral arteries. This device dilates occluded vessels while causingminimal trauma to the lesion thus minimizing the risk of dissections,total occlusion, abrupt closure and restenosis, and promotes fasterhealing.

A Constraining Structure (CS) is placed over a balloon catheter whereupon inflation both the balloon and the CS increase in diameter andduring deflation the CS returns to its original dimensions. The CS canhave multiple designs intended to expand to a diameter smaller than themaximal inflated diameter of the balloon. The CS can be connected to theballoon either on the distal side or the proximal side or both. It canalso float over the balloon without firm attachment using simple coverssince the CS can be designed to maintain its length during expansion andtherefore there is no relative axial movement between the CS and theballoon. It can be made from various materials, processes and designs.It can be made from metal, preferable a very elastic metal such asNitinol and it can be made from variety of polymers (e.g. Nylon). It canbe constructed from wires or laser cut from a tube, sheath or otherforms of materials.

In a preferred embodiment of this invention the CS is over the balloon.During inflation the CS expands allowing the balloon to expand under it.The maximum CS diameter is smaller than that of the inflated balloon,thus the balloon protrudes and expands through the CS creating atopography of hills and valleys. The CS structure creates a combinationof a designed topography and controlled, slower inflation promoting aprocess of plaque remodeling. The plaque in the diseased area of thevessel is able to flow through the valleys in the designed topography,and re-distribute in the vessel allowing a gradual inflation without theneed to apply added pressure.

Referring to FIGS. 4A to 4C, in a conventional balloon during inflation,due to balloon compliance, the balloon will expand toward areas of lessresistance (healthy areas or areas with less plaque buildup—see FIG.4B). In order to successfully dilate the lesion additional pressureshould be applied until the lesion areas with more severe blockageyields and the balloon can inflate entirely (see FIG. 4C). This processis abrupt and aggressive exposing vessel wall (healthy or diseasedareas) to severe trauma and may result in dissection, restenosis and aslower healing process. The topography created by the CS allows for theplaque to gradually re-disperse and flow through the CS valleys (seeFIGS. 2A and 2B) while the catheter expands and the inflation is gradualand controlled. The design of the CS allows for plaque remodelingcreating less trauma and promotes faster healing.

In one embodiment of this invention, the CS is attached to both ends ofthe balloon and is capable of maintaining a constant length duringinflation and deflation processes. During inflation the CS structureexpands to a pre-designed diameter that is smaller than the ballooninflated diameter. The balloon continues to expand beyond the CS but isrestricted in length by the CS structure. Referring to FIG. 2B, theballoon inflates through the CS structure and is restricted in length bythe CS design, thus allowing the device to be inflated without balloonlengthening (common in conventional balloons) thus reducing oreliminating axial forces applied on vessel wall and minimizing trauma tovessel. Furthermore this allows more predictability in inflationprocess. This is especially effective in long balloons (commonly used inperipheral arteries).

In one embodiment of this invention the CS is constructed of radialrings connecting by axial wires. Upon inflation the CS expands radiallywithout any axial lengthening. This structure allows a compartmentalinflation process where the rings create separate inflation zones withinthe vessel. Therefore the pressure to the vessel wall is controlled andis applied in the radial direction without any strain in the axialdirection reducing trauma and possible dissections.

The present invention can be utilized to deliver various agents oractive substances particularly (but not limited to) those suitable fortreating vascular and other luminal conditions such as antiproliferativeand antimitotic agents (such as paclitaxel and sirolimus) othersubstances can include antibiotics, antiplatelet agents hormones andmore.

The active substance can be placed in various designs or techniques suchas directly coated on the balloon surface, the CS or both. It can beembedded in a matrix/carrier placed on the balloon or the CS or both.The combination of low trauma dilatation with release of active agentcan be superior to drug eluting stents for some portions of thepopulation by minimizing the need for a permanent implant yet providinggood long term results.

In one embodiment the balloon surface is coated with drug. Upon ballooninflation, the ‘pillows’/hills formed in the balloon external surfacecoated with drug engage the vessel wall and compress the drug into thewall to facilitate efficient drug delivery to the treated site.

Drug delivery can be facilitated using many different design methodsincluding but not limited to coating the balloon, coating the CSstructure or both. Coating with a drug directly or using a carrier in aform of a matrix or microcapsules.

1.-15. (canceled)
 16. A system for performing angioplasty comprising: acatheter shaft; an inflatable balloon at a distal portion of thecatheter shaft; and a radially expandable constraining structuredisposed over the balloon, the constraining structure comprising: aplurality of axially spaced-apart, radially expandable rings; and aplurality of circumferentially spaced-apart axial struts crossing theplurality of rings, the constraining structure being non-deployablydisposed over the balloon; wherein, when the balloon is inflated, amaximum expanded diameter of the constraining structure is less than amaximum inflated diameter of the balloon, such that separate inflationzones separated by the plurality of rings and the plurality of strutsare created, the separate inflation zones being positioned radiallyoutward of the constraining structure.
 17. The system of claim 16,wherein the constraining structure is configured to restrict a length ofthe balloon during inflation.
 18. The system of claim 16, wherein aproximal end or a distal end of the constraining structure is attachedto the catheter shaft.
 19. The system of claim 16, wherein proximal anddistal ends of the constraining structure are attached to the cathetershaft.
 20. The system of claim 16, wherein, prior to inflation, theballoon is folded beneath the constraining structure.
 21. The system ofclaim 16, wherein each of the plurality of rings is a fully enclosedring.
 22. The system of claim 16, wherein the plurality of rings areconfigured to expand independently of each other.
 23. The system ofclaim 16, wherein, prior to the balloon being inflated, the constrainingstructure has an initial diameter, and wherein, when the balloon isdeflated, the constraining structure returns to the initial diameter.24. The system of claim 16, wherein the constraining structure comprisesa drug coating.
 25. The system of claim 16, wherein the ballooncomprises a drug coating.
 26. The system of claim 16, wherein theconstraining structure comprises wires.
 27. The system of claim 16,wherein the constraining structure is laser cut.
 28. The system of claim16, wherein the constraining structure comprises a metal.
 29. The systemof claim 16, wherein the constraining structure comprises a polymer. 30.A method for deploying a balloon catheter, the method comprising:advancing a balloon catheter comprising a constraining structurenon-deployably disposed over a balloon to a target site in a vessel of apatient; and inflating the balloon such that the balloon protrudes andexpands through windows in the constraining structure, the constrainingstructure restricting axial lengthening of the balloon during inflation.31. The method of claim 30, wherein inflating the balloon includescausing the constraining structure to expand.
 32. The method of claim30, further comprising delivering an active substance to the vessel. 33.The method of claim 30, wherein inflating the balloon includes causingthe balloon to unfold.